There are various methods for curing a silicone composition, including a condensation reaction catalized by organic metal compounds, a vulcanization catalized by organic peroxides and a hydrosilylation catalized by platinum group metal catalysts. However, these curing methods need heating. It is desired to improve productivity and to save energy that curing takes place at room temperature.
In recent years, curing with radiation draws attention as a method for providing an energy for curing without heating. This curing method includes polymerization of acrylic compounds by a radical polymerization, and an ene-thiol reaction. Particularly, a cation-polymerizable organopolysiloxane which is cured via a ring-opening reaction of epoxy group with generation of an acid does not receive inhibition of its curing by oxygen, and a cation-polymerizable organopolysiloxane is convenient and has good handling property, so that the applications are expanding. Further, the cation-polymerizable organopolysiloxane does not need a heat for a curing reaction and, therefore, can be applied on film substrates which have poor heat resistance. Therefore, the cation-polymerizable organopolysiloxane is used as a backside-treating agent of adhesive tapes, a coating agent for release paper for adhesive labels and a coating agent for fixing fastener tapes.
Japanese Patent Application Laid-Open No. Sho 50-151997 and Japanese Patent Nos. 2623426, 3384268 and 3993533 describe compositions comprising an epoxy group-containing cation-polymerizable organopolysiloxane and a photoacid generator which causes generation of acid by radiation, as a composition which cures by cation polymerization.
Further, cation-polymerizable organopolysiloxanes are used as a releasing agent for adhesive tapes of sanitary supplies such as sanitary napkins and disposable diapers. The sanitary napkin and the disposable diaper are individually packaged in view of usability and sanitation. Particularly, an individual packaging film for a sanitary napkin has a film, such as a polyethylene film, which is provided with a releasing agent. The film provided with a releasing agent is attached on an adhesive layer of a main body of the napkin, which adhesive layer fixes the napkin on an underwear and, then, the napkin is wrapped and packaged. The radiation-curable silicone composition is often used as the releasing agent.
Japanese Patent No. 2987524 describes an invention for a sanitary napkin and a sheet for individually packaging a sanitary napkin wherein a release agent layer is formed on one side of a base material. The aforesaid release agent layer is obtained by curing a release agent mainly comprising an epoxy-functional polyorganosiloxane with ultraviolet irradiation, and the epoxy-functional polyorganosiloxane has 1 to 20 mole % of a monovalent epoxy-functional organic group, relative to a total mole of the organic groups. Even if this sheet for individually packaging sanitary napkins is exposed to a light source such as the sun or a fluorescent before used, the force needed for releasing the sheet from the adhesive layer does not increase, and the sheet can be easily peeled from the napkin when it is used.
Japanese Patent No. 3638850 describes a sheet having a high antistick effect against dirt, wherein a layer of a first silicone compound is formed on a surface of a base sheet, and a layer of a second silicone compound whose surface tension is lower than that of the first silicone compound is further formed on the surface of the layer of the first silicone compound. Thus, this sheet is coated with the two silicone compounds which have different surface tensions to form a sheet having a multi-layer construction and a high effect of antistick effect against dirt.
The sanitary napkin is often provided a smell with a perfume, but customers diversify in the recent years and, therefore, a request for an odorless sanitary napkin is increasing. Therefore, a main part of the napkin and an adhesive layer are needed to be odorless and, further, an individual packaging film provided with a releasing agent, which is released before using the main part of the napkin, is also needed to be odorless because the individual packaging film is also touched with a customer. When a composition comprising a cation-polymerizable organopolysiloxane and a photoacid generator is used as a radiation-curable silicone composition to form a cured product, odor of an epoxy group as the cation-polymerizable group and odor of a photoacid generator as a curing catalyst tend to remain a little. However, none of the aforesaid patent literatures mention odor of the silicone layer.
Japanese Patent Application Laid-Open No. Hei 11-104166 describes a releasing film for individual packaging of sanitary goods, wherein at least one surface of a synthetic resin film is release treated and an adhesive surface is exposed in air. The releasing layer is composed of a releasing agent made by curing a photo-curing composition containing an epoxy-modified silicone and an optical cation-polymerization initiator. In this film, odor is avoided by the use of the cation-polymerizable organopolysiloxane in the releasing agent. However, the cation-polymerizable organopolysiloxane is not specified and, therefore, odor of an epoxy group and odor of a photoacid generator are not completely prevented. Decrease of odor from the film is not sufficient.
Thus, almost no invention is known for decrease of odor of a releasing layer of an individual packaging of a sanitary napkin.
Regarding an invention for decreasing odor of a cation-polymerizable organopolysiloxane composition, Japanese Examined Patent Publication No. Hei 6-49848 describes an ultraviolet-curable organopolysiloxane release coating composition, which is substantially odorless. The composition comprises                (A) a poly(epoxy haloaryl alkyl siloxane) selected from the group consisting of (i) an epoxy haloaryl alkyl siloxane consisting essentially of approximately 20 to 100 condensation siloxy units selected from diorganosiloxy units represented by (R)2SiO, epoxyorganosiloxy units represented by RR1SiO and haloaryl alkyl siloxy units represented by RR2SiO, and (ii) a blend of the component (i) and an epoxy siloxanes consisting essentially of approximately 20 to 100 condensation siloxy units selected from approximately 88 to 99 mole % of diorganosiloxy units and approximately 5 to 12 mole % of epoxy organosiloxy units, and components (i) or (ii) is present in amounts enough to provide approximately 76 to 94 mole % of diorganosiloxy units, approximately 5 to 12 mole % of epoxyorganosiloxy units and approximately 1 to 12 mole % of haloaryl alkylsiloxy units, and        (B) an effective amount of a polyaryl onium hexafluorometalloid salt selected from a diarylidonium salt and a triarylsulfonium salt.        
An epoxy group-containing organopolysiloxane having a monovalent phenol group is known as a release-adjusting agent. It was confirmed that the epoxy group-containing organopolysiloxane had odor of allylphenol remaining in the siloxanes. Patent Literature 8 describes that odor is prevented by the use of a compound having a methyl-chlorophenyl ethyl siloxy unit and a methylepoxy cyclohexyl siloxy unit as the release-adjusting agent.
Japanese Examined Patent Publication No. Hei 6-17447 describes a method for providing a controlled releasing property on paper or a plastic substrate. This method comprises steps of                (A) paper or a plastic substrate is treated with an ultraviolet-curable epoxy silicone mixture, and        (B) the treated substrate is subjected to curing with ultraviolet to form a tack-free adhesive film having no stain, wherein the ultraviolet-curable epoxy silicone mixture comprises        (C) 100 parts by weight of an epoxy silicone comprising 5 to 12 mole % of condensation epoxy organo siloxy units, based on total moles of the condensation diorganosiloxy units        (D) an effective amount of a photosensitive polyaryl onium hexafluorometalloid salt, and        (E) 0.1 to 50 parts by weight of one kind of a the specific additive selected from the group consisting of (1) alkyl phenols having 8 to 20 carbon atoms and (ii) phenol alkyl-substituted organodisiloxanes.        
Japanese Patent No. 5081826 describes a method for preparing a silicone release coating on a base material.
The method comprises                (a) a step of preparing a silicone coating composition which cross-links and/or polymerizes with irradiation of short wave ultraviolet (UV-C) having a wavelength in a range of 200 and 280 nm;        (b) a step of coating a base material with the aforesaid silicone coating composition; and        (c) a step of irradiating the aforesaid base material coated with the aforesaid silicone coating composition with at least one low-pressure lamp which emits false monochromatic light in the aforesaid UV-C region to polymerize the composition,wherein the aforesaid composition comprises        (A) at least one of liquid polyorganosiloxane monomer, oligomer and/or polymer A, which have a viscosity of approximately 10 to 10000 mPa·s at 25 degrees C. and comprises at least one functional group, Fa, which cross-links and/or polymerizes via a cation route, and        (B) an effective amount of a cationic photoinitiator or a radical photoinitiator, which are active under the aforesaid UV-C radiation, wherein the functional group, Fa, is selected from the group consisting of epoxy, oxetane and dioxisoran functional groups.        